This invention relates to a machining device such as an which suffers from the decomposed gas and oil mist which may be produced during machining.
FIGS. 6 and 7 are a longitudinal sectional view and a plan view, respectively, showing an example of a conventional electrical discharge machine. In those figures, reference numeral 1 designates a machining vessel; 2, a workpiece in the machining vessel 1; 3, an electrode for machining the workpiece 2 by electric discharge; 4, the machining solution in the machining vessel 1: 5, decomposed gas of the machining solution which is produced in discharge machining; 6, the oil mist formed by vaporizing the machining solution at room temperature; 7, an air jetting unit provided above the machining vessel 1; 8, the stream of air produced by the air jetting unit 7; 9, an air sucking inlet 9 for sucking the stream of air thus produced; and 10, an air sucking unit.
In the conventional electrical discharge machine thus constructed, the decomposed gas 5 produced by electric discharging and the oil mist formed at room temperature are caused to flow on the stream of air formed above the machining vessel 1 into the air sucking inlet, thus being suitably processed.
As was described above, the air jetting unit 7 is installed above the machining vessel 1. Therefore, the stream of air produced by the air jetting unit 7 is merely a laminar stream. In an electric discharge machining operation, the level of the machining solution in the machining vessel changes depending on the size of the workpiece therein. Depending on the level of the machining solution, the decomposed gas hazardous to the human body cannot be detected immediately when it appears over the machining solution; that is, it is detected when dispersed fully in the machining vessel. It is difficult to detect the decomposed gas which is located near the walls of the machining vessel.
In this case, in order to increase the rate of detection of the decomposed gas, it is necessary to increase the pressure of the air jetting unit thereby to increase the speed of flow of the air. However, the method of increasing the air jetting pressure is disadvantageous in that the electrical discharge machine is increased in equipment cost, and an electrical discharge machining operation cannot be achieved with high accuracy because the machine is locally changed in temperature.